Is the adverse drug reaction you’re experiencing actually due to the drug you took?

The Naranjo Scale is a questionnaire for determining the likelihood of whether an adverse drug reaction is actually due to the drug or caused by other factors. Probability is assigned via a score termed definite, probable, possible or doubtful.*

YES

NO

UNKOWN

Are there previous conclusive reports on this reaction?

Did the adverse event appear after the suspected drug was administered?

Did the adverse reaction improve when the drug was discontinued or a specific antagonist was administered?

Did the adverse reaction reappear when the drug was readministered?

Are there alternative causes (other than the drug) that could on their own have caused the reaction?

Did the reaction reappear when a placebo was given?

Was the drug detected in the blood (or other fluids) in concentrations known to be toxic?

Was the reaction more severe when the dose was increased, or less severe when the dose was decreased?

Did the patient have a similar reaction to the same or similar drugs in any previous exposure?